Thermosensitive recording media are ordinarily prepared by mixing together a colorless or pale-colored electron donating leuco dye and an electron accepting color developing agent, such as a phenolic compound and the like, after grinding them into fine particles, preparing a coating solution by adding a binder, a filler, a sensitivity enhancing agent, a slipping agent and other aids to the mixture and applying the coating solution onto a substrate such as paper, synthetic paper, film, plastic and the like. Thermosensitive recording medium develops color through an instantaneous chemical reaction when heated using a thermal head, hot stamp, hot pen, laser light and the like and yields a recorded image. Thermosensitive recording media are used extensively in recording media such as facsimile devices, computer terminal printers, automatic ticket dispensers, recorders for meters, receipts at super markets and convenience stores and the like.
In recent years, the use of thermosensitive recording media is expanding, such as its use for various ticket, receipts, labels, ATM of Bank, meter reading of gas and electricity, cash vouchers, such as car racing or horseracing betting. Among these applications, for example, in such as ticket and cash vouchers, it is preferred that the thermosensitive recording medium has a high gloss surface to produce a feeling of luxury. Furthermore, among these applications, especially in meter reading of gas and electricity, the demand for high speed printing is increasing.
It has been practiced to form the outermost layer of a thermosensitive recording medium by cast coating method in order to increase the gloss of the surface of the thermosensitive recording medium (Reference 1, etc.). However, when improving the smoothness of the outermost layer of the thermosensitive recording medium in order to increase the gloss of its surface, the thermosensitive material in the thermosensitive recording medium melts to stick to the thermal head when printing, which deteriorates the printing run-ability. This is called as stick problem. To solve this problem, it has been practiced to contain a slipping agent, such as zinc laurate, in the outermost layer of the thermosensitive recording medium (Reference 2, etc.). It is also practiced to form a gloss layer as the outermost layer containing a slipping agent and a polysiloxane-grafted acrylic resin to improve the gloss and the anti-sticking property (Reference 3, etc.).
Meanwhile, it is known to contain a carboxyl group-containing resin in the outermost layer of the thermosensitive recording medium to improve water resistance etc. (Reference 4, etc.).
Reference 1: Japanese Patent Application Public Disclosure H10-217609
Reference 2: Japanese Patent Application Public Disclosure 2010-214728
Reference 3: Japanese Patent Application Public Disclosure H5-246140
Reference 4: International Publication WO2011/145545